This invention relates in general to the field of railway car trucks and more particularly to a railway car truck satisfactory for use with a railway car having a gross weight on rail rating of three hundred and fifteen thousand pounds (315,000 lbs) and overall dimensions and weight substantially the same as current railway car trucks used with railway cars having gross weight on rail ratings of two hundred and eighty six thousand pounds (286,000 lbs).
Most modern railway cars include a pair of railway car trucks with each railway car truck having a pair of axles. Typically, a pair of wheels are secured to each axle with the wheels spaced from each other a distance corresponding with the gauge of the associated railway tracks. A pair of roller bearing assemblies are generally mounted on each axle to reduce friction and to allow the axle and associated wheels to rotate with a minimum amount of applied force. A railway truck axle typically includes a shaft with a wheel seat and journal formed adjacent to opposite ends of the shaft. A wheel is secured to each wheel seat. Respective journals extend from each wheel seat for mounting respective bearing assemblies adjacent to each end of the railway truck axle. Each bearing assembly is preferably tightly fitted on its respective journal. Each bearing assembly typically includes a housing or adapter. Portions of each side frame of the associated railway car truck are engaged with and supported by respective bearing housings. The journals often have the smallest diameter of the railway truck axle and the wheel seats often have the largest diameter.
A railway car truck typically includes a bolster or main transverse member which transmits loads from an associated railway carbody to respective side frames through a suspension system. The associated carbody typically engages the truck bolster through a truck center plate which is generally aligned with and contacts the associated carbody center plate. Side bearings may also be disposed between the truck bolster and carbody. A typical truck center plate includes a generally circular area designed to accept a protruding center plate from the associated carbody. The truck center plate provides the principal bearing surface to support the carbody on the truck bolster. Truck center plates are often fitted with a horizontal wear plate and a vertical wear ring to improve wear characteristics and extend the service life of the associated truck bolster.
The different size capacity of Association of American Railroads (AAR) standard freight car trucks are commonly indicated by nominal or rated load carrying capacity of a railway car equipped with such trucks. Typical truck size indications are 40 ton, 50 ton, 70 ton, 100 ton, and 125 ton. A more specific indication of truck size is the total allowable gross weight on rail of a railway car equipped with the particular size truck. Examples of such truck size indications are 142,000 lbs, 177,000 lbs, 220,000 lbs, 263,000 lbs, and 315,000 lbs respectively. Since 1994, AAR standard freight car trucks for have been commercially available for gross weight on rail railway cars with 286,000 pound ratings.
Total allowable or maximum gross weight on rail for a railway truck is generally determined by the capacity of the journal bearings on the associated railway truck axles. Also, associated with each nominal railway car truck size is a given wheel diameter size to limit maximum wheel/rail contact stress. Examples of typical journal bearing sizes and wheel sizes for AAR standard freight car trucks are included in the following table.
Total allowable or maximum gross weight on rail may also be referred to as xe2x80x9cgross rail loadxe2x80x9d (GRL), xe2x80x9ctotal allowable gross weight on the railsxe2x80x9d or xe2x80x9cmaximum gross weight on the rails.xe2x80x9d
Before a railway car truck having a nominal size of one hundred tons may be used on a railway car rated for more than two hundred and sixty three thousand pounds gross weight on rail, the railway car truck must be designed and tested for the resulting increased loads. Prior to 1994, railway car trucks having a nominal truck size of one hundred tons were generally limited to a maximum gross weight on rail rating of two hundred and sixty three thousand pounds. At the present time, railway car trucks having a nominal truck size of one hundred tons are available for use on railway cars rated for two hundred and eighty six thousand pounds gross weight on rail.
Modifications to existing freight car truck designs to improve load carrying capability and/or service life are generally limited due to standard AAR classifications which require interchangeability of component parts. Also, the resulting railway car must meet applicable AAR operating envelopes.
In accordance with teachings of the present invention, railway car trucks are provided for use with a railway car having a maximum gross weight on rail rating of 315,000 pounds and substantially improved performance when compared to prior AAR approved railway car trucks for 315,000 pound gross weight on rail rated railway cars. One aspect of the present invention includes providing a railway car truck having a frame assembly, a suspension system, a pair of axles, bearing assemblies and wheels satisfactory for use with a railway car having a 315,000 pound gross weight on rail rating. Various modifications have been made to a railway truck incorporating teachings of the present invention to increase load carrying capacity, to reduce fretting and/or wear of various components and to increase fatigue life of various components.
Technical benefits of the present invention include providing a railway car truck rated for use with a railway car having approximately 315,000 pounds gross weight on rail at an initial cost and life cycle cost substantially equal to or less than current AAR approved railway car trucks used with 286,000 pound gross weight on rail rated railway cars. A railway car truck incorporating teachings of the present invention may be used with existing car bodies having dimensions and clearances which are only suitable for use with AAR nominal size 100 ton trucks. By combining existing car bodies with railway car trucks incorporating teachings of the present invention, the resulting railway cars may carry substantially heavier loads while satisfying current AAR operating envelopes and specifications.
Further technical benefits of the present invention include providing a railway car truck rated for 315,000 pound gross weight on rail application having wheels with diameters less than thirty-eight inches (38xe2x80x3) and a weight equal to or less than the weight of wheels used on railway car trucks rated for 286,000 pounds gross weight on rail application. A railway car truck incorporating teachings of the present invention also includes wheels having thermal and mechanical capabilities equal to or better than wheels associated with current railway car trucks rated for 286,000 pound gross weight on rail and current railway car trucks rated for 315,000 pounds gross weight on rail. The shape of the wheels increases thermal capacity and reduces mechanical stresses. The thickness of the rim on each wheel is preferably limited to approximately one and five-eighths inches (1⅝xe2x80x3) to reduce the overall weight of the wheel. For some applications, providing a rim which is approximately one and five-eighths inches thick may reduce the weight of the wheels by approximately twenty pounds. A railway car truck incorporating teachings of the present inventions preferably includes wheels having hub inside diameters larger than the inside diameter of normal thirty six inch (36xe2x80x3) diameter wheels to prevent placing the wheels on a railway car truck which is not rated for 315,000 pounds gross weight on rail.
Still further technical benefits of the present invention include providing a railway car truck satisfactory for use with a railway car having a rating of more than approximately 286,000 pounds gross weight on rail to as much as 315,000 pounds gross weight on rail or larger with:
bearing assemblies having a life expectancy substantially equal to the life expectancy of the associated wheels;
a longitudinal wheel base approximately equal to five feet ten inches;
axle fatigue life equivalent to the fatigue life of axles on current AAR approved trucks used with railway cars having ratings of 286,000 pounds gross weight on rail;
bolster and side frame fatigue life equivalent to the fatigue life of bolsters and side frames on current AAR approved trucks used with railway cars having ratings of 286,000 pounds gross weight on rail;
satisfactory for use with both truck mounted and body mounted brake systems;
complies with current AAR specifications for hunting and curving;
weight approximately the same as the weight of current AAR approved trucks used with railway cars having a rating of 286,000 pounds gross weight on rail;
operating performance equal to or better than current AAR approved trucks used with railway cars having a rating of 286,000 pounds gross weight on rail; and
initial cost and life cycle cost substantially equal to or less than current AAR approved trucks used with railway cars having a rating of 286,000 pounds gross weight on rail.